Thirteen patients with recurrent or new primary gynecologic malignancies after previous radiation therapy (RT) underwent interstitial reirradiation (IRI) from July 1986 through December 1990. Mean and median ages were 63 and 70 years, respectively. Mean and median implanted volumes were 14.3 and 12 cc, respectively. Overall, 9/13 (69%) had complete responses to IRI and 6 (46%) continue to have no evidence of disease (NED) 24-71 months later (median follow-up, 59 months). Of 7 patients with recurrent cervical or new primary vaginal carcinoma, 5 (71%) remain free of disease 27-71 months (median, 58 months) after IRI. Of 6 patients with recurrent endometrial carcinomas, only 1 (16%) continues with NED 24 months after IRI. Patients with NED after IRI had a median disease-free interval prior to IRI of 100 months compared to 6 months in patients failing IRI. Trends toward improved outcomes were observed in squamous vs adenocarcinoma, smaller tumor volumes, higher implant doses, and vaginal wall/suburethra vs vaginal cuff location. One possible complication, a rectovaginal fistula, developed in the presence of recurrent cervical cancer 22 months after IRI. Interstitial reirradiation is an effective treatment for selected patients with recurrent gynecologic malignancies after previous RT. Advantages of IRI over radical surgery include its potential to preserve organ structure and function and its applicability to patients with medical contraindications to salvage surgery. Furthermore, since subsequent exenterative surgery should not be compromised in patients failing IRI, a policy of IRI as initial treatment may be justified for patients in whom the potential for morbidity is limited.